Mitsubishi Montero (2002-2004). Manual - part 638

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DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-249

STEP 14. Check the left bank heated oxygen sensor (rear).
(1) Disconnect the left bank heated oxygen sensor (rear)

connector C-15 and connect test harness special tool,
MD998464, to the connector on the left bank heated oxygen
sensor (front) side.

(2) Warm up the engine until engine coolant 80

°C (176°F) or

higher.

CAUTION

Be very careful when connecting the jumper wires; incor-
rect connection can damage the left bank heated oxygen
sensor (rear).

(3) Use the jumper wires to connect terminal No. 1 (red clip) to

the positive battery terminal and terminal No. 3 (blue clip) to
the negative battery terminal.

(4) Connect a digital volt meter between terminal No. 2 (black

clip) and terminal No. 4 (white clip).

(5) While repeatedly revving the engine, measure the left bank

heated oxygen sensor (rear) output voltage.

Standard value: 0.6

− 1.0 volt

Q: Is the voltage between 0.6 and 1.0 volt?

YES : Replace the PCM. Then go to Step 15.
NO : Replace the left bank heated oxygen sensor (rear).

Then go to Step 15.

STEP 15. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to

GROUP 13A, Procedure 6

− Other Monitor

P.13Ab-2

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0156 set?

YES : Retry the troubleshooting.
NO : The inspection is complete.

AK201280

CONNECTOR: C-15

C-15(B)

HARNESS
CONNECTOR:
COMPONENT SIDE

RIGHT BANK
HEATED OXYGEN
SENSOR (REAR)

AKX01625AC

BLUE

RED

BLACK

JUMPER
WIRES

WHITE

MD998464

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DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-250

DTC P0157: Heated Oxygen Sensor Circuit Low Voltag (bank 2, sensor 2)

WHITE

ACK

WHITE

ACK

AK201137

TO PCM

FROM MFI RELAY

116

4 5 6

E-112

LEFT BANK
HEATED OXYGEN
SENSOR (REAR)

POWERTRAIN CONTROL
MODULE (PCM)

1 2

C-15

MU802605

23 24 25 26

20 21 22

27 28 29 30 31 32 33

10 11

D-116

1
5

7 8

3 4
9 10

2
6

D-14

MU801335

Left Bank Heated Oxygen Sensor (rear) Circuit

9192

939495

96979899

100

105

113114

115116117

118119120

106

107108109

110111112

101102103

104

D-135

(MU803805)

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DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-251

CIRCUIT OPERATION

• A voltage corresponding to the oxygen concen-

tration in the exhaust gas is sent to the PCM (ter-
minal No. 116) from the output terminal
(terminalNo. 4) of the left bank heated oxygen
sensor (rear).

• Terminal No. 2 of the left bank heated oxygen

sensor (rear) is grounded with PCM (terminal No.
96).

TECHNICAL DESCRIPTION

• The output signal of the left bank heated oxygen

sensor (front) is compensated by the output sig-
nal of the left bank heated oxygen sensor (rear).

• The PCM checks for an open circuit in the left

bank heated oxygen sensor (rear) output line.

DTC SET CONDITIONS

Check Conditions

• 3 minutes or more have passed since the starting

sequence was completed.

• Left bank heated oxygen sensor (rear) signal volt-

age has continued to be 0.15 volt or lower.

• Engine coolant temperature is higher than 76°C

(169

°F).

• Engine speed is higher than 1,200 r/min.

• Volumetric efficiency is higher than 25 percent.

• Volume airflow sensor output frequency is 100 Hz

or more.

• At least 20 seconds have passed since fuel shut

off control was canceled.

• The left bank heated oxygen sensor (front) out-

puts 0.5 volts or more.

• After the ignition switch is turned ON, the

changes in the output voltage of the left bank
heated oxygen sensor (rear) is lower than 0.078
volt.

AK201279

CONNECTOR: C-15

C-15(B)

RIGHT BANK
HEATED OXYGEN
SENSOR (REAR)

AK201049

CONNECTOR: D-116

D-116

AK201052

E-112

CONNECTOR: E-112

AK201038AF

CONNECTOR: D-135

PCM

D-135(GR)

AK201049

D-14

CONNECTOR: D-14

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DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-252

• Monitoring time: 10 seconds.

Judgement Criteria

• Making the air/fuel ratio 15 percent for 10 sec-

onds richer does not result in raising the left bank
heated oxygen sensor (rear) output voltage
beyond 0.15 volt.

• The PCM monitors for this condition once during

the drive cycle.

TROUBLESHOOTING HINTS (The most likely
causes for this code to be set are: )

• Left bank heated oxygen sensor (rear) failed.

• Short circuit in left bank heated oxygen sensor

(rear) output line.

• PCM failed.

DIAGNOSIS

Required Special Tools:

• MB991502: Scan Tool (MUT-II)

• MB998464: Test Harness Set

STEP 1. Using scan tool MB991502, check data list item 59:
Heated Oxygen Sensor Bank 2, Sensor 2 (left bank).

CAUTION

To prevent damage to scan tool MB991502, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991502.
(1) Connect scan tool MB991502 to the data link connector.
(2) Start the engine and run at idle.
(3) Set scan tool MB991502 to the data reading mode for item

59, Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).

• Warming up the engine. When the engine is revved, the

output voltage should repeat 0 volt and 0.6 to 1.0 volt
alternately.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?

YES : It can be assumed that this malfunction is intermittent.

Refer to GROUP 00, How to Use Troubleshooting/
Inspection Service Points

P.00-6

NO : Go to Step 2.

ACX01539

16-PIN

MB991502

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